Showing Error while sending Email when clicking "ask about this product"

[vaibhour]

Hi,
I am working on a site www.setmiindia.in. I have installed Virtuemart 2.0 a while ago. I Faced a problem while clicking "Ask about this product" and writing an email. When I try to send it always shows an error:-

Fatal error: Call to undefined function mb_strlen() in /home/setmiind/public_html/components/com_virtuemart/controllers/productdetails.php on line 78...

Also whenever I try to edit product details in frontend it again shows an error:-

Fatal error: Call to a member function getProduct() on a non-object in /home/setmiind/public_html/components/com_virtuemart/views/productdetails/view.html.php on line 78

Please try to solve it asap.